We all know the nightmare scenario: a bunch of sexually savvy five-year-olds wander the streets in strappy tops and miniskirts, winking knowingly at anyone who walks past.

This, according to the right-wing press, is what we have to fear if compulsory sex education is introduced in primary schools.

Such end-of-the-civilised-world projections are usually accompanied by frenzied denials from the other side. “We’re not talking about that kind of sex-education,” they say. “We’re talking about feelings and emotions. Being nice to other people, respecting yourself. We don’t get on to the actual how-to-have-sex stuff until they’re practically 21.”

But let’s go the other way for a change. Let’s imagine that plans to introduce sex education in primary schools did involve teaching five-year-olds how babies are made. Also that sex is not just about making babies, but can be a fun game for grown-ups. Like bridge, only lying down.

Five-year-olds hear a lot of implausible truths. You can tell them that humans are related to monkeys, and they’ll believe you. You can tell them that if you dig straight through the Earth you’ll reach Australia, and they’ll nod and reach for a spade.

Similarly, you can tell them that mummy and daddy have sex to show how much they love each other, and they might think about it for a moment, then go back to doing something more interesting - such as digging to Australia.

Five-year-olds don’t realise that sex is supposed to be more interesting or controversial than art or science or any other subject. So talking about sex early and often merely normalises it. It doesn’t make children want to go out and sleep with everyone they meet. That comes later, when teenage hormones start percolating - and the hormones will percolate, no matter how much or how little sex education teenagers have received.

Sex education - internalised at an early age - can make all the difference when it comes to having sex safely.Adi Bloom, Social affairs reporter.